Acoustic neuroma

Causes

Acoustic neuromas have been linked with the genetic disorder neurofibromatosis type 2 (NF2).

Acoustic neuromas are uncommon.

Symptoms

The symptoms vary based on the size and location of the tumor. Because the tumor grows so slowly, symptoms usually start after age 30.

Common symptoms include:

• Abnormal feeling of movement (vertigo)
• Hearing loss in the affected ear that makes it hard to hear conversations
• Ringing (tinnitus) in the affected ear

Less common symptoms include:

• Difficulty understanding speech
• Dizziness
• Headache 
• Loss of balance
• Numbness in the face or one ear
• Pain in the face or one ear
• Weakness of the face

Exams and Tests

The health care provider may suspect an acoustic neuroma based on your medical history, an examination of your nervous system, or tests.

Often, the physical exam is normal when the tumor is diagnosed. Sometimes, the following signs may be present:

• Decreased feeling on one side of the face
• Drooping on one side of the face
• Unsteady walk

The most useful test to identify an acoustic neuroma is an MRI of the brain. Other tests to diagnose the tumor and tell it apart from other causes of dizziness or vertigo include:

• Hearing test (audiology)
• Test of equilibrium and balance (electronystagmography)
• Test of hearing and brainstem function (brainstem auditory evoked response)

Treatment

Treatment depends on the size and location of the tumor, your age, and your overall health. You and your health care provider must decide whether to watch the tumor (observation), use radiation to stop it from growing, or try to remove it.

Many acoustic neuromas are small and grow very slowly. Small tumors with few or no symptoms may be followed, especially in older patients. Regular MRI scans will be done.

If they are not treated, some acoustic neuromas can damage the nerves involved in hearing and balance, as well as the nerves responsible for movement and feeling in the face. Very large tumors can lead to a buildup of fluid (hydrocephalus) in the brain, which can be life-threatening.

Removing an acoustic neuroma is more commonly done for:

• Larger tumors
• Tumors that are causing symptoms
• Tumors that are growing quickly
• Tumors that are pressing on the brain

Surgery is done to remove the tumor and prevent other nerve damage. Any hearing that is left is often lost with surgery.

Stereotactic radiosurgery focuses high-powered x-rays on a small area. It is considered to be a form of radiation therapy, not a surgical procedure. It may be used:

• To slow down or stop the growth of tumors that are hard to remove with surgery
• To treat patients who are unable to have surgery, such as the elderly or people who are very sick

Removing an acoustic neuroma can damage nerves, causing loss of hearing or weakness in the face muscles. This damage is more likely to occur when the tumor is large.

Outlook (Prognosis)

An acoustic neuroma is not cancer. The tumor does not spread (metastasize) to other parts of the body. However, it may continue to grow and press on important structures in the skull.

People with small, slow-growing tumors may not need treatment.

Once hearing loss occurs, it does not return after surgery or radiosurgery.

Possible Complications

• Brain surgery can completely remove the tumor in most cases.
• Most people with small tumors will have no permanent paralysis of the face after surgery. However, about two-thirds of patients with large tumors will have some permanent weakness of the face after surgery.
• About one-half of patients with small tumors may still be able to hear in the affected ear after surgery.
• There may be delayed radiation effects after radiosurgery, including nerve damage, loss of hearing, and paralysis of the face.

When to Contact a Medical Professional

Call your health care provider if you  have: 

• Hearing loss that is new or getting worse
• Ringing in one ear
• Dizziness (vertigo)

Alternative Names

Vestibular schwannoma; Tumor - acoustic; Cerebellopontine angle tumor; Angle tumor

References

Baloh RW, Jen J. Hearing and equilibrium. In: Goldman L, Schafer AI, eds. Cecil Medicine. 24th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 430.

Brackmann DE, Arriaga MA. Neoplasms of the posterior fossa. In: Cummings CW, Flint PW, Haughey BH, et al, eds. Otolaryngology: Head & Neck Surgery. 5th ed. Philadelphia, Pa: Mosby Elsevier;2010:chap 177.

Battista RA. Gamma knife radiosurgery for vestibular schwannoma. Otolaryngol Clin North Am. 2009;42:635-654.

Sweeney P, Yajnik S, Hartsell W, Bovis G, Venkatesan J. Stereotactic radiotherapy for vestibular schwannoma. Otolaryngol Clin North Am. 2009;42:655-663.

Conley GS, Hirsch BE. Stereotactic radiation treatment of vestibular schwannoma: indications, limitations, and outcomes. Curr Opin Otolaryngol Head Neck Surg. 2010 Oct;18(5):351-6.

Update Date: 5/22/2012

Updated by: Linda J. Vorvick, MD, Medical Director and Director of Didactic Curriculum, MEDEX Northwest Division of Physician Assistant Studies, Department of Family Medicine, UW Medicine, School of Medicine, University of Washington; and Seth Schwartz, MD, MPH, Otolaryngologist, Virginia Mason Medical Center, Seattle, Washington. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M. Health Solutions, Ebix, Inc.